New user, 1st attempt failed, backup uses WinRAR files?

I’m a totally frustrated new My Book owner.

Just purchased 5 TB version from BestBuy yesterday (Model #WDBFJK0050HBK-NESN)

Computer using Windows 7 Ultimate OS

Followed limited/vague instructions for My Book and started backup.
After letting run overnight, I got up this morning and it was done… but there was an error message that the backup failed.

I looked at the files, and to my surprise, they are all WinRAR archive files… is this correct?

The drive started with 4.54 TB and now has 3.95 TB free. I was saving approximately 900 GB worth of date, don’t know if this would be “condensed” using WinRAR?

I am also surprised to not find my 5 TB My Book listed on the website, and when I type in the model #, nothing comes up.

This a very frustrating and bad experience… thinking of just returning this and getting a Seagate product.

According to this message, it is a Best Buy exclusive model.